Characterising atmospheric cloud particles using spatial light scattering

To be able to understand the radiative transfer properties of ice and mixed phase (ice and water) clouds, a detailed knowledge of the cloud particles' shapes and sizes is required, along with measurements of the number concentration of ice and super-cooled liquid particles (Foot 1988; Arnott et al. 1994). In addition, measurement of the total ice crystal number is important to facilitate the testing of theories of the nucleation of ice crystals and their interaction with aerosol particles. This paper describes progress of the development of a new aircraft mounted instrument for use in cloud and aerosol microphysical research where particle size and shape are important parameters, such as in the discrimination between supercooled water droplets and ice crystals of I-25pm size within cirrus clouds, (virtually impossible to achieve with current instrumentation).